Conveyors used in dishwashing machines and dish collection and distribution systems are either a continuously running type such as disclosed in U.S. Pat. No. 4,004,682 or U.S. Pat. No. 3,237,755; or a continually running type with a manual or automatic stop motion mechanism, which stops the conveyor when an article being carried is obstructed.
Some conveyor chains are adapted to travel in a straight line and the connecting links are capable of movement in a vertical plane. Other conveyor chains are capable of movement in a horizontal plane. Further conveyor chains are available in which their links are pinned for movement in both horizontal and vertical planes. Some conveyor chains form an integral part of a total structure such as disclosed in U.S. Pat. No. 2,829,726. U.S. Pat. Nos. 3,768,631 and 2,328,504 each teach conveyor chains adapted for movement in two directions, which chains directly support the object to be carried. U.S. Pat. Nos. 3,334,726 and 3,237,755 are both directed to endless chains for movement in a vertical plane. U.S. Pat. No. 3,382,097 and British Patent Specification No. 767,567 appear to be the closest prior art references.
In commercially available conveyor chains for dishwashing systems, the racks in which are placed the dishes, utensils, flatware, etc. to be cleaned, are engaged by the conveyor chain and the conveyor chain carries the racks through a plurality of stations such as a pre-rinse station, a wash station, a final rinse station, etc. In some embodiments as disclosed above, the chain is used solely as a drive mechanism and the racks ride along tracks. In other systems and in the one in which the present invention is directed, the chain itself rides on a conveyor pan at least through a portion of its journey and while riding on the conveyor pan, the weight of the rack is substantially carried by the conveyor chain. Thus, the conveyor chain functions both as a drive mechanism and as a support mechanism. In systems of this type, there is of course wear between the conveyor pan and the conveyor chain particularly on the non-linear portion of the pan, i.e. where the chain turns a corner.
With these systems, the links of the conveyor chain turn about a vertical axis and the conveyor chain moves solely in a horizontal plane. The conveyor travels through both linear and non-linear portions. When the conveyor chain travels in the non-linear portion, it tends to move radially outward causing lateral sliding friction. This results in substantially increased wear on the conveyor pan in such non-linear portions and corresponding increased wear of the conveyor chain.
The present invention is directed to a conveyor chain adapted to turn solely in a horizontal plane wherein the links are pinned and turn about a vertical axis. Further, the invention is directed to the type of conveyor chain which is supported by a conveyor pan.
The conveyor chain embodying the invention has a plurality of links, each of the links having a pair of opposed non-parallel wheels or rollers, which are fixed to a link in a manner to overcome or compensate for the increased radial forces incurred when the conveyor chain moves through a non-linear section on the conveyor pan; thus, minimizing substantially the wear on a conveyor pan and correspondingly, the conveyor chain.
Broadly, the invention comprises a dishwasher conveyor chain having a plurality of links, each link including a shell portion having an upper surface, a planar tab extending forwardly of the shell portion and a planar tab extending rearwardly of the shell portion; the shell having opposed wall sections lying in planes which extend outwardly and downwardly with reference to the upper surface, wheels rotatably secured outwardly and downwardly with reference to the upper surface, the wheels adapted to engage a bearing surface and to travel along a non-linear path in a horizontal plane to minimize lateral sliding friction, the rearward tab of a first link rotatably pinned to the forward tab of a second link for relative movement about a vertical axis.
In the preferred embodiment of the invention, the axis of rotation of the wheels lie in the same plane and intersect. In an alternative embodiment, the wheels may be offset from one another such that their axes lie in distinct planes. If desired, a first shell may carry a first wheel on one side, a second succeeding shell may carry a second wheel on another side, etc.
Lastly, a drive wheel especially suited for the conveyor chain is provided. The drive wheel functions both to drive the chain and to deflect the chain toward the conveyor pan during arcuate travel.